Comparative Analysis of Bacterial and Archaeal Communities in Methanogenic Sludge Granules from Upflow Anaerobic Sludge Blanket Reactors Treating Various Food-Processing, High-Strength Organic Wastewaters

Abstract

A comprehensive survey of bacterial and archaeal community structures within granular sludges taken from twelve different types of full-scale, food-processing wastewater-treating, upflow anaerobic sludge blanket (UASB) reactors was performed with a 16S rRNA gene-based clone library method. In total, 1,282 bacterial 16S rRNA gene clones and 722 archaeal clones were analyzed, and their identities were determined by phylogenetic analyses. Overall, clones belonging to the bacterial phyla Proteobacteria (the class Deltaproteobacteria in particular), Firmicutes, Spirochaetes, and Bacteroidetes were observed in abundance within the bacterial clone libraries examined, indicating common bacterial denominators in such treatment systems. Within the domain Archaea, clones affiliated with the classes Methanomicrobia and Methanobacteria were found to be abundant in the archaeal libraries. In relation to features of reactor performance (such as chemical oxygen demand removal, fatty acid accumulation, and sludge bulking), possible representative phylotypes likely to be associated with process failures, such as sludge bulking and the accumulation of propionate, were found in comparative analyses of the distribution of phylotypes in the sludge libraries.Key words: 16S rRNA gene clone library, granular sludge, microbial community, UASB Anaerobic digestion technology has been used effectively to treat organic matter in waste streams. To date, various anaerobic processes for treating wastewater have been developed (1,29,32). One of the most established technologies in this field is the upflow anaerobic sludge blanket (UASB) system, because of its ability to treat a broad range of organic waste streams at high loading rates (32,40,45,47). The most characteristic phenomenon in this process is sludge granulation, i.e., granular-shaped sludge is spontaneously formed within the system. Granular sludge generally has superior settling characteristics. Thus, the stable and efficient operation of granular sludge-based systems is primarily dependent on the growth and maintenance of granular sludge. Granular sludge is also characterized as a spherical biofilm, possessing all the trophic groups of anaerobes necessary for the complete mineralization of organic matter. Owing to its characteristic internal structure, granular sludge is also important for the efficient biotransformation of organic matter into methane (48).Understanding the ecology of anaerobes involved in granular sludge is essential to the control of these bioreactors. The microbiology of granular sludges in UASB bioreactors has been studied using culture-dependent and molecularbased approaches, particularly those targeting 16S rRNA genes (38,45,47). So far, molecular-based community analyses have been performed for UASB granular sludges treating wastewater from a paper factory (41), a terephthalatemanufacturing plant (53), a beer brewery (13), and sucrose/ propionate/acetate-based artificial wastewater (44). In addition, the molecular characterization of UASB granules targeting s...

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